Heretofore, supply boats and similar vessels have typically been moored to offshore drilling and/or production platforms and similar structures utilizing catenary-type mooring systems. Although adequate for shallow water applications, catenary-type mooring systems are unsatisfactory for use in deep water applications.
One problem associated with the use of catenary-type systems to affect bow mooring of supply boats and similar vessels involves the repetitive flexing of the components of the mooring system on or near the sea floor due to the action of tides, waves, currents, etc. The flexing of the component parts of a catenary-type mooring system results in increased wear, which in turn results in reduced service life of the system. This problem is compounded by the fact that the flexing of the component parts of a catenary-type mooring system is most pronounced in the components of the system situated near the sea floor. Thus, when a catenary-type mooring system is used in deep water, it is impossible for divers to descend deep enough to inspect and repair the component parts of the system which are the most subject to wear. Currently, a deep water catenary mooring system is typically inspected at 12 to 24 month intervals by retrieving the system, inspecting the system on board the retrieving vessel, and replacing worn components.
A more significant problem attendant to the use of catenary-type bow mooring systems in deep water applications involves the fact that catenary-type mooring systems do not provide sufficient stiffness to prevent the moored vessel from drifting too close to the adjacent structure. Because the catenary-type mooring system cannot apply sufficient force to keep the vessel properly positioned relative to the adjacent structure, the propulsion system of the vessel must be regularly used to keep the vessel clear of the adjacent structure. Present mooring systems are not satisfactory due to the increased costs of fuel consumption to operate the supply vessel's propulsion system and the risk of collision with the platform in case of a propulsion failure due to human error or equipment problems.